1. Field of the Invention
The present invention relates to a developer restoring unit freely detachable to the image forming apparatus such as electrophotographic copying machines and various printers, the image forming apparatus comprising an image bearing member, means for forming latent image corresponding to image information on the surface of the image bearing member, means for developing the latent image on the surface of the image bearing member by developer, means for transferring the developed image onto recording means, a cleaner for removing the developer left on the surface of the image bearing member after the developed image transferrring process, and means for conveying the developer from the cleaner to the developing means, wherein at least the developing means, cleaner and means for conveying the developer from the cleaner to the developing means are combined with one another to form the developer restoring unit.
More particularly, the present invention relates to a developer restoring unit in which the developer conveyor means is provided with a means for preventing the developer from flowing backward from the developing means to the clearner before the unit is set to the image forming apparatus.
2. Description of the Related Art
Such developer restoring unit sometimes includes photosensitive drum which serves as the image bearing member.
Image forming apparatuses, which have the above described construction but in which developer-backflow preventing is not mounted in the developer restoring unit, have been well known from U.S. Pat. No. 3,752,576 and U.S. Pat. No. 4,323,306.
The developer restoring unit is shipped from its factory and put on the market, independently of the other various components of the image froming apparatus. A predetermined amount of developer has already been contained in the developing means of the developer restoring unit at the time when the unit is to be shipped from the factory. In a case where the unit includes no developer-backflow preventing means, therefore, the developer flows backward from the developing means to the developer conveying means and even to the cleaner when the unit is roughly treated on the way of its shipment or circulation in the market.
When it flows backward like this, the developer becomes insufficient in the developing means and this causes the image forming apparatus to sound alarm, telling that the developer is insufficient, when the developer restoring unit is set in the image forming apparatus. When developer is supplied responsive to the alarm, however, the amount of developer becomes excessive in the whole of the developer restoring unit, thereby causing the unit not to be operated as requested and making it difficult to control the density of images transferred on the recording means. In a case where the developer consists of various elements, the ratio of these elements in the developer restoring unit changes to make it impossible to well transfer image on the recording means.
When the images forming apparatus is operated, even if no alarm is sounded, under such a condition that the developer in the developing means is insufficient, image cannot be well transferred on the recording means.
In a case where the developer restoring unit includes the developer-backflow preventing means, the above-mentioned drawbacks are not caused even if the unit is roughly treated on the way of its shipment or circulation in the market.
Image forming apparatuses in which the developer restoring unit includes the developer-backflow preventing means have been well known from the published and unexamined Japanese Patent Application Nos. 63-71864 and 63-29776, for example.
An adhesive seal disclosed in the former and serving as the developer-backflow preventing means, however, the manually seal peeling work is troublesome and likely to be forgotten just before the developer restoring unit is set in the image forming apparatus.
A develope-backflow preventing means disclosed in the later must be manually operated just after the developer restoring unit is set in the image forming apparatus, but its manual operation is troblesome. In addition, the mechanism for manually operating the developer-backflow preventing means is so large-sized as to need large space.